Because of his business trip, he can only join the meeting online.
Tips
usage
线上 (xiànshàng, 'online') vs 线下 (xiànxià, 'offline / in-person') is a productive pair: 线上活动 (online events), 线下门店 (brick-and-mortar stores), 线上线下结合 (online-offline integration). Use this pair instead of borrowing English 'online'.
culture
Workplace tools have shifted heavily to domestic platforms: 钉钉 (DingTalk, by Alibaba) and 腾讯会议 (Tencent Meeting) dominate corporate online meetings in China. Zoom is much less common after 2020.
